MS SQL Server Can not Startup

1.Whether changed the password of OS

  The changing of OS (login password or security policy) can reflect on SQL Server to startup.

  1). Control Panel à Administrative Tools à Services à MSSQLSERVER à Properties à Log On à Log on as à Select "Local System account".
Or
  2). Control Panel à Administrative Tools à Services à MSSQLSERVER à Properties à Log On à Log on as à Select "This account", input the changed password.

  The base reason is that Sql server is not the access to reading or modifying the files in the folders. 

2.Whether changed computer name
  If changed the computer name, we need to repair Sql Server using the installation CD.

3.Whether the version of SQL Server is evaluation or not.
  We can install Sql sp3 to check whether it is evaluation.